Thrust bearings have been used for a long time for many purposes and are used essentially for absorbing axial thrust loads. According to the specific application, different variants are known, with these being directed predominantly for the requirement of the least possible installation space as well as the realization as a compact and preferably closed structural unit. In this respect, for examples refer to the publications U.S. Pat. No. 2,891,828, U.S. Pat. No. 4,981,373, DE 36 43 584 A1, DE 38 40 957 A1, and DE 39 14 175 A1.
Thrust bearings are also used in known automatic transmissions in motor vehicles, for example, for axial support of the sun wheel on a planet carrier of a planetary gear unit. However, in practice it has been shown that for conventional standard bearings, as disclosed, for example, by the above-noted publications, lubricant can flow radially through the thrust bearing and, in a disadvantageous way, is no longer available or only in a quantity that is too little for the actual purpose, namely a defined axial supply to the differential gear unit of the motor vehicle.
It was further recognized that during the operation of an automatic transmission, in planetary gear construction, an axial thrust load is generated on the sun wheel of the planetary gear, by means of which this sun wheel can move away from the thrust bearing, possibly in the axial direction. This state is noted only when driving in forward gears (when idling or driving in reverse gear, a thrust force is generated in the reverse direction), but due to these conditions, lubricant can also flow away radially in an undefined way through open spaces between the thrust bearing and the corresponding support surfaces. This is where the invention described below begins.